Abstract
This experimental investigation deals with the influence of turbulence intensities Tu δ ⩽13% and a ratio of integral length scale Λ 11 to boundary layer thickness δ 99.5 smaller than two on an axisymmetric turbulent boundary layer with zero pressure gradient. The free-stream turbulence was generated by jets injected normal to the flow upstream of the test section. The boundary layer had a Reynolds number range 1000⩽ Re δ 2 ⩽2700. Skin-friction measurements were performed using oil-film interferometry, Preston tubes and wall hot-wire probes. Mean and fluctuating velocities were measured by hot-wire anemometry and Reynolds stresses, triple correlations and spectra were evaluated. The free-stream turbulence increases the skin friction by up to 34% and considerably changes both mean and fluctuating velocity distributions in the outer region of the boundary layer.
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